Numerous systems relating to containing, communicating with and locating children are presently available. Such systems, however, typically do not include all of the aforementioned capabilities. For example, U.S. Pat. No. 4,136,338 (Antenore) discloses a perimeter alarm apparatus including a loop of wire that is placed within the ground so as to define the area in which the child is to be contained and electrical circuitry connected to the loop to detect the absence of a signal imposed on the loop. A sending unit is worn by the child and produces a signal that is imposed on the loop. If the child is within the defined area, the sending unit induces a signal on the loop. When the child moves beyond the loop by a predetermined distance, no signal is imposed on the loop and an alarm is sounded. In the aforementioned patent, the signal is imposed on the loop by a sending unit worn by the child, rather than by a radio frequency transmitter under the control of the child's parent. In addition, means for communicating with the child or for determining the location of the child if the child leaves the defined area is not provided under the aforementioned patent.
U.S. Pat. No. 5,661,460 (Sallen et al.) discloses a distance determination and alarm system comprised of a plurality of transceiver units, one transceiver unit being in the possession of the parent and the other transceiver unit being worn by the child. The system produces an alarm when the transceiver unit worn by the child is more than a predetermined distance away from the transceiver unit in the possession of the parent. The distance is determined by the difference in the phase of a reference signal that is transmitted on a radio frequency signal by the parent's transceiver unit, then received and retransmitted by the child's transceiver unit, and then received again by the parent's transceiver unit. This patent does not include any means for containing the child within a predetermined area and/or means for communicating with the child or locating the child.
U.S. Pat. No. 5,289,163 (Perez et al.) discloses a child locating device consisting of two transceiver units. The child's transceiver unit generates a signal that is received by the parent's transceiver unit. If the signal generated by the child's transceiver unit becomes weak as the result of the child exceeding a predetermined distance from the parent's transceiver unit, an alarm is sounded by the parent's transceiver unit to alert the parent that the child has wandered away. The parent's transceiver unit also has a direction indicator function to assist in locating the child. This patent, however, makes no provision for containing the child within a predetermined area.
U.S. Pat. No. 5,812,056 (Law) discloses a wireless child monitoring and locating device consisting of a transmitter worn by the child and a receiver in the possession of the parent. The parent's receiving unit is capable of detecting when the child strays beyond a predetermined distance from the parent. This patent makes no reference to means for containing the child with a predetermined area and/or means for communicating with the child or for locating the child if the child leaves a predetermined area.
In view of the foregoing, it has become desirable to develop a system for containing a child within a defined area, communicating with that child when the child is within the defined area or outside the defined area, and for locating the child when the child has strayed from the defined area, using a wire loop located in the ground.